Aluminum alloy wire rod, aluminum alloy stranded wire, coated wire, wire harness and manufacturing method of aluminum alloy wire rod

ABSTRACT

An aluminum alloy wire rod comprising 0.1-1.0 mass % Mg; 0.1-1.0 mass % Si; 0.01-1.40 mass % Fe; 0.01-0.50 mass % Zr; 0.000-0.100 mass % Ti; 0.000-0.030 mass % B; 0.00-1.00 mass % Cu; 0.00-0.50 mass % Ag; 0.00-0.50 mass % Au; 0.00-1.00 mass % Mn; 0.00-1.00 mass % Cr; 0.00-0.50 mass % Hf; 0.00-0.50 mass % V; 0.00-0.50 mass % Sc; 0.00-0.50 mass % Co; and 0.00-0.50 mass % Ni, a Mg/Si ratio being greater than 1, wherein a dispersion density of an Mg 2 Si compound having a particle size of 0.5 μm to 5.0 μm is less than or equal to 3.0×10 −3  particles/μm 2 , and in the sectional structure, a concentration of each of Mg and Si other than a compound is less than or equal to 2.00 mass %.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 15/073,204 filed Mar. 17, 2016, which is a continuation-in-partof U.S. patent application Ser. No. 14/681,742 filed Apr. 8, 2015, whichis a continuation application of International Patent Application No.PCT/JP2013/080955 filed Nov. 15, 2013, which claims the benefit ofJapanese Patent Application No. 2013-075403, filed Mar. 29, 2013, thefull contents of all of which are hereby incorporated by reference intheir entirety.

BACKGROUND

Technical Field

The present disclosure relates to an aluminum alloy wire rod used as aconductor of an electric wiring structure, an aluminum alloy strandedwire, a coated wire, a wire harness, and a method of manufacturing analuminum alloy wire rod, and particularly relates to an aluminum alloywire rod that has an improved impact resistance and bending fatigueresistance while ensuring strength, elongation and conductivityequivalent to the related art products, even when used as an extra finewire having a strand diameter of less than or equal to 0.5 mm.

Background

In the related art, a so-called wire harness has been used as anelectric wiring structure for transportation vehicles such asautomobiles, trains, and aircrafts, or an electric wiring structure forindustrial robots. The wire harness is a member including electric wireseach having a conductor made of copper or copper alloy and fitted withterminals (connectors) made of copper or copper alloy (e.g., brass).With recent rapid advancements in performances and functions ofautomobiles, various electrical devices and control devices installed invehicles tend to increase in number and electric wiring structures usedfor devices also tends to increase in number. On the other hand, forenvironmental friendliness, lightweighting of transportation vehicles isstrongly desired for improving fuel efficiency of transportationvehicles such as automobiles.

As one of the measures for achieving lightweighting of transportationvehicles, there have been, for example, continuous efforts in thestudies of using aluminum or aluminum alloys as a conductor of anelectric wiring structure, which is more lightweight, instead ofconventionally used copper or copper alloys. Since aluminum has aspecific gravity of about one-third of a specific gravity of copper andhas a conductivity of about two-thirds of a conductivity of copper (in acase where pure copper is a standard for 100% IACS, pure aluminum hasapproximately 66% IACS), an aluminum conductor wire rod needs to have across sectional area of approximately 1.5 times greater than that of acopper conductor wire rod to allow the same electric current as theelectric current flowing through the copper conductor wire rod to flowthrough the pure aluminum conductor wire rod. Even an aluminum conductorwire rod having an increased cross section as described above is used,using an aluminum conductor wire rod is advantageous from the viewpointof lightweighting, since an aluminum conductor wire rod has a mass ofabout half the mass of a pure copper conductor wire rod. Note that, “%IACS” represents a conductivity when a resistivity 1.7241×10⁻⁸ Ωm ofInternational Annealed Copper Standard is taken as 100% IACS.

However, it is known that pure aluminum wire rods, typically an aluminumalloy wire rod for transmission lines (JIS (Japanese IndustrialStandard) A1060 and A1070), is generally poor in its durability totension, resistance to impact, and bending characteristics. Therefore,for example, it cannot withstand a load abruptly applied by an operatoror an industrial device while being installed to a car body, a tensionat a crimp portion of a connecting portion between an electric wire anda terminal, and a cyclic stress loaded at a bending portion such as adoor portion. On the other hand, an alloyed material containing variousadditive elements added thereto is capable of achieving an increasedtensile strength, but a conductivity may decrease due to a solutionphenomenon of the additive elements into aluminum, and because ofexcessive intermetallic compounds formed in aluminum, a wire break dueto the intermetallic compounds may occur during wire drawing. Therefore,it is essential to limit or select additive elements to providesufficient elongation characteristics to prevent a wire break, and it isfurther necessary to improve impact resistance and bendingcharacteristics while ensuring a conductivity and a tensile strengthequivalent to those in the related art.

For example, aluminum alloy wire rods containing Mg and Si are known ashigh strength aluminum alloy wire rods. A typical example of thisaluminum alloy wire rod is a 6xxx series aluminum alloy (Al—Mg—Si basedalloy) wire rod. Generally, the strength of the 6xxx series aluminumalloy wire rod can be increased by applying a solution treatment and anaging treatment. However, when manufacturing an extra fine wire such asa wire having a wire size of less than or equal to 0.5 mm using a 6xxxseries aluminum alloy wire rod, although the strength can be increasedby applying a solution heat treatment and an ageing treatment, theelongation tends to be insufficient.

For example, Japanese Laid-Open Patent Publication No. 2012-229485discloses a conventional 6xxx series aluminum alloy wire used for anelectric wiring structure of the transportation vehicle. An aluminumalloy wire disclosed in Japanese Laid-Open Patent Publication No.2012-229485 is an extra fine wire that can provide an aluminum alloywire having a high strength and a high conductivity, as well as animproved elongation. Also, Japanese Laid-Open Patent Publication No.2012-229485 discloses that good elongation results in improved bendingcharacteristics. However, for example, it is neither disclosed norsuggested to use an aluminum alloy wire as a wire harness attached to adoor portion, and there is no disclosure or suggestion about impactresistance or bending fatigue resistance under an operating environmentin which a fatigue fracture is likely to occur due to repeated bendingstresses exerted by opening and closing of the door.

The present disclosure is related to providing an aluminum alloy wirerod used as a wire rod of an electric wiring structure, an aluminumalloy stranded wire, a coated wire, a wire harness, and a method ofmanufacturing an aluminum alloy wire rod that has an improved impactresistance and bending fatigue resistance at an ordinary temperaturewhile ensuring strength, elongation and conductivity equivalent to thoseof a product of the related art (aluminum alloy wire disclosed inJapanese Laid-Open Patent Publication No. 2012-229485), when it is aprerequisite to use an aluminum alloy containing Mg and Si, bysuppressing segregation where a difference in concentration of eachadded element occurs inside crystal grains or at grain boundaries in aparent phase (e.g., intra-granular segregation or grain boundarysegregation) due to added elements including Mg and Si as majorcomponents, and particularly even when used as an extra fine wire havinga strand diameter of less than or equal to 0.5 mm, and further, has anexcellent bending fatigue resistance in a high temperature environment.

The present inventors have observed a microstructure of the aluminumalloy wire rod of the related art containing Mg and Si, and found that aportion in which Mg- and Si-concentrations are high is formed in aparent phase including grain boundaries. Therefore, the presentinventors have carried out assiduous studies under the assumption thatdue to existence of a portion in which Mg- and Si-concentrations arehigh in a parent phase, an interface bonding between a portion in whichMg- and Si-concentrations are high and an aluminum parent phase is weak,which results in a decrease in a tensile strength, elongation, impactresistance and bending fatigue resistance. The present inventors haveprepared various types of aluminum alloy wire rods with theconcentrations of Mg and Si existing in the parent phase being varied bycontrolling a manufacturing process and having a composition in which aMg/Si ratio is greater than 1 and Zr is an essential component, andcarried out a comparison. As a result, it was found that, in a casewhere a portion where Mg- and Si-concentrations are high was formedneither inside crystal grains nor at grain boundaries in the parentphase, an improved impact resistance, bending fatigue resistance at anordinary temperature and bending fatigue resistance in a hightemperature environment can be achieved while ensuring strength,elongation and conductivity equivalent to a product of the related art(aluminum alloy wire disclosed in Japanese Laid-Open Patent PublicationNo. 2012-229485), and contrived the present disclosure.

SUMMARY

According to a first aspect of the present disclosure, an aluminum alloywire rod has a composition comprising 0.1 mass % to 1.0 mass % Mg; 0.1mass % to 1.0 mass % Si; 0.01 mass % to 1.40 mass % Fe; 0.01 mass % to0.50 mass % Zr; 0.000 mass % to 0.100 mass % Ti; 0.000 mass % to 0.030mass % B; 0.00 mass % to 1.00 mass % Cu; 0.00 mass % to 0.50 mass % Ag;0.00 mass % to 0.50 mass % Au; 0.00 mass % to 1.00 mass % Mn; 0.00 mass% to 1.00 mass % Cr; 0.00 mass % to 0.50 mass % Hf; 0.00 mass % to 0.50mass % V; 0.00 mass % to 0.50 mass % Sc; 0.00 mass % to 0.50 mass % Co;and 0.00 mass % to 0.50 mass % Ni, a Mg/Si ratio being greater than 1,wherein a dispersion density of an Mg₂Si compound having a particle sizeof 0.5 μm to 5.0 μm is less than or equal to 3.0×10⁻³ particles/μm², andin a sectional structure, a concentration of each of Mg and Si otherthan a compound is less than or equal to 2.00 mass %.

According to a second aspect of the present disclosure, a wire harnessincludes a coated wire including a coating layer at an outer peripheryof one of an aluminum alloy wire rod and an aluminum alloy strandedwire, the aluminum alloy stranded wire comprising a plurality of thealuminum alloy wire rods which are stranded together; and a terminalfitted at an end portion of the coated wire, the coating layer beingremoved from the end portion, the aluminum alloy wire rod having acomposition comprising 0.1 mass % to 1.0 mass % Mg, 0.1 mass % to 1.0mass % Si; 0.01 mass % to 1.40 mass % Fe; 0.01 mass % to 0.50 mass % Zr;0.000 mass % to 0.100 mass % Ti; 0.000 mass % to 0.030 mass % B; 0.00mass % to 1.00 mass % Cu; 0.00 mass % to 0.50 mass % Ag; 0.00 mass % to0.50 mass % Au; 0.00 mass % to 1.00 mass % Mn; 0.00 mass % to 1.00 mass% Cr; 0.00 mass % to 0.50 mass % Hf; 0.00 mass % to 0.50 mass % V; 0.00mass % to 0.50 mass % Sc; 0.00 mass % to 0.50 mass % Co; and 0.00 mass %to 0.50 mass % Ni, a Mg/Si ratio being greater than 1, wherein adispersion density of an Mg₂Si compound having a particle size of 0.5 μmto 5.0 μm is less than or equal to 3.0×10⁻³ particles/μm², and in asectional structure, a concentration of each of Mg and Si other than acompound is less than or equal to 2.00 mass %.

According to a third aspect of the present disclosure, a method ofmanufacturing an aluminum alloy wire rod according to the first aspectof the disclosure, the aluminum alloy wire rod being obtained by forminga drawing stock through hot working subsequent to melting and casting,and thereafter carrying out processes including a first wire drawingprocess, a first heat treatment process, a second wire drawing process,a second heat treatment process and an aging heat treatment process inthis order, wherein the first heat treatment process includes, afterheating to a predetermined temperature within a range of 480° C. to 620°C., cooling at an average cooling rate of greater than or equal to 10°C./s at least to a temperature of 150° C., and the second heat treatmentincludes, after heating to a predetermined temperature within a range ofnot less than 300° C. but less than 480° C. for less than two minutes,cooling at an average cooling rate of greater than or equal to 9° C./sat least to a temperature of 150° C.

The aluminum alloy wire rod of the present disclosure is based on aprerequisite to use an aluminum alloy containing Mg and Si, and bysuppressing segregation where a difference in concentration of eachadded element occurs inside crystal grains or at grain boundaries in aparent phase (e.g., intra-granular segregation or grain boundarysegregation) due to added elements including Mg and Si as majorcomponents, particularly when used as an extra fine wire having a stranddiameter of less than or equal to 0.5 mm, an aluminum alloy wire rodused as a conductor of an electric wiring structure, an aluminum alloystranded wire, a coated wire, a wire harness, and a method ofmanufacturing an aluminum alloy wire rod can be provided with animproved impact resistance and bending fatigue resistance at an ordinarytemperature, and further with an improved bending fatigue resistance ina high temperature environment, while ensuring strength, elongation andconductivity equivalent to those of a product of the related art(aluminum alloy wire disclosed in Japanese Laid-Open Patent PublicationNo. 2012-229485), and thus it is useful as a conducting wire for amotor, a battery cable, or a harness equipped on a transportationvehicle, and as a wiring structure of an industrial robot. Particularly,since an aluminum alloy wire rod of the present disclosure has a hightensile strength, a wire size thereof can be made smaller than that ofthe wire of the related art, and it can be appropriately used for adoor, a trunk or a hood requiring a high impact resistance, bendingfatigue resistance at an ordinary temperature and bending fatigueresistance in a high temperature environment.

DETAILED DESCRIPTION

An aluminum alloy wire rod of the present disclosure has a compositioncomprising 0.1 mass % to 1.0 mass % Mg; 0.1 mass % to 1.0 mass % Si;0.01 mass % to 1.40 mass % Fe; 0.01 mass % to 0.50 mass % Zr; 0.000 mass% to 0.100 mass % Ti; 0.000 mass % to 0.030 mass % B; 0.00 mass % to1.00 mass % Cu; 0.00 mass % to 0.50 mass % Ag; 0.00 mass % to 0.50 mass% Au; 0.00 mass % to 1.00 mass % Mn; 0.00 mass % to 1.00 mass % Cr; 0.00mass % to 0.50 mass % Hf; 0.00 mass % to 0.50 mass % V; 0.00 mass % to0.50 mass % Sc; 0.00 mass % to 0.50 mass % Co; and 0.00 mass % to 0.50mass % Ni; Mg/Si ratio being greater than 1, wherein a dispersiondensity of an Mg₂Si compound having a particle size of 0.5 μm to 5.0 μmis less than or equal to 3.0×10⁻³ particles/μm², and, in a sectionalstructure, a concentration of each of Mg and Si other than a compound isless than or equal to 2.00 mass %.

Herein, a compound is a substance in which two or more elements arechemically bonded, and in general, has a higher hardness and lowerelectric conductivity than an aluminum parent phase that is bondedthrough metallic bonding. Since a compound has a crystal structuredifferent from that of the aluminum parent phase, it can bedistinguished from an aluminum parent phase by studying an X-raydiffraction pattern.

Hereinafter, reasons for limiting chemical compositions or the like ofthe aluminum alloy wire rod of the present disclosure will be described.

(1) Chemical Composition

<Mg: 0.10 Mass % to 1.00 Mass %>

Mg (magnesium) is an element having a strengthening effect by forming asolid solution with an aluminum base material and a part thereof havingan effect of improving a tensile strength, a bending fatigue resistanceand a heat resistance by being combined with Si to form precipitates.However, in a case where Mg content is less than 0.10 mass %, the aboveeffects are insufficient. In a case where Mg content exceeds 1.00 mass%, there is an increased possibility that, in sectional structure, aconcentration of Mg other than a compound exceeds 2.00 mass %, thusresulting in decreased tensile strength, elongation, and bending fatigueresistance, as well as a reduced conductivity due to an increased amountof Mg element forming the solid solution. Accordingly, the Mg content is0.10 mass % to 1.00 mass %. The Mg content is, when a high strength isof importance, preferably 0.50 mass % to 1.00 mass %, and in case wherea conductivity is of importance, preferably 0.10 mass % to 0.50 mass %.Based on the points described above, 0.30 mass % to 0.70 mass % isgenerally preferable.

<Si: 0.10 Mass % to 1.00 Mass %>

Si (silicon) is an element that has an effect of improving a tensilestrength, a bending fatigue resistance and a heat resistance by beingcombined with Mg to form precipitates. However, in a case where Sicontent is less than 0.10 mass %, the above effects are insufficient. Ina case where Si content exceeds 1.00 mass %, there is an increasedpossibility that, in a sectional structure, a concentration of Si otherthan a compound exceeds 2.00 mass %, thus resulting in decreased tensilestrength, elongation, and fatigue resistance, as well as a reducedconductivity due to an increased amount of Si element forming the solidsolution. Accordingly, the Si content is 0.10 mass % to 1.00 mass %. TheSi content is, when a high strength is of importance, preferably 0.50mass % to 1.00 mass %, and in case where a conductivity is ofimportance, preferably 0.10 mass % to 0.50 mass %. Based on the pointsdescribed above, 0.30 mass % to 0.70 mass % is generally preferable.

<Fe: 0.01 Mass % to 1.40 Mass %>

Fe (iron) is an element that contributes to refinement of crystal grainsmainly by forming an Al—Fe based intermetallic compound and providesimproved tensile strength and bending fatigue resistance. Fe dissolvesin Al only by 0.05 mass % at 655° C. and even less at room temperature.Accordingly, the remaining Fe that could not dissolve in Al will becrystallized or precipitated as an intermetallic compound such as Al—Fe,Al—Fe—Si, and Al—Fe—Si—Mg. This intermetallic compound contributes torefinement of crystal grains and provides improved tensile strength andbending fatigue resistance. Further, Fe has, also by Fe that hasdissolved in Al, an effect of providing an improved tensile strength. Ina case where Fe content is less than 0.01 mass %, those effects areinsufficient. In a case where Fe content exceeds 1.40 mass %, a wiredrawing workability worsens due to coarsening of crystallized materialsor precipitates. As a result, a target bending fatigue resistance cannotbe achieved and also a conductivity decreases. Therefore, Fe content is0.01 mass % to 1.40 mass %, and preferably 0.15 mass % to 0.90 mass %,and more preferably 0.15 mass % to 0.45 mass %.

The aluminum alloy wire rod of the present disclosure includes Mg, Si,Fe and Zr as essential components, and may further contain at least oneselected from a group consisting of Ti and B, and/or at least oneselected from a group consisting of Cu, Ag, Au, Mn, Cr, Hf, V, Sc, Coand Ni, as necessary.

<Ti: 0.001 Mass % to 0.100 Mass %>

Ti is an element having an effect of refining the structure of an ingotduring dissolution casting. In a case where an ingot has a coarsestructure, the ingot may crack during casting or a wire break may occurduring a wire rod processing step, which is industrially undesirable. Ina case where Ti content is less than 0.001 mass %, the aforementionedeffect cannot be achieved sufficiently, and in a case where Ti contentexceeds 0.100 mass %, the conductivity tends to decrease. Accordingly,the Ti content is 0.001 mass % to 0.100 mass %, preferably 0.005 mass %to 0.050 mass %, and more preferably 0.005 mass % to 0.030 mass %.

<B: 0.001 Mass % to 0.030 Mass %>

Similarly to Ti, B is an element having an effect of refining thestructure of an ingot during dissolution casting. In a case where aningot has a coarse structure, the ingot may crack during casting or awire break is likely to occur during a wire rod processing step, whichis industrially undesirable. In a case where B content is less than0.001 mass %, the aforementioned effect cannot be achieved sufficiently,and in a case where B content exceeds 0.030 mass %, the conductivitytends to decrease. Accordingly, the B content is 0.001 mass % to 0.030mass %, preferably 0.001 mass % to 0.020 mass %, and more preferably0.001 mass % to 0.010 mass %.

To contain at least one of <Cu: 0.01 mass % to 1.00 mass %>, <Ag: 0.01mass % to 0.50 mass %>, <Au: 0.01 mass % to 0.50 mass %>, <Mn: 0.01 mass% to 1.00 mass %>, <Cr: 0.01 mass % to 1.00 mass %>, and <Zr: 0.01 mass% to 0.50 mass %>, <Hf: 0.01 mass % to 0.50 mass %>, <V: 0.01 mass % to0.50 mass %>, <Sc: 0.01 mass % to 0.50 mass %>, <Co: 0.01 mass % to 0.50mass %>, and <Ni: 0.01 mass % to 0.50 mass %>.

Each of Cu, Ag, Au, Mn, Cr, Zr, Hf, V, Sc, Co and Ni is an elementhaving an effect of refining crystal grains, and Cu, Ag and Au areelements further having an effect of increasing a grain boundarystrength by being precipitated at a grain boundary. In a case where atleast one of the elements described above is contained by 0.01 mass % ormore, the aforementioned effects can be achieved and a tensile strength,an elongation, and a bending fatigue resistance can be further improved.On the other hand, in a case where any one of Cu, Ag, Au, Mn, Cr, Zr,Hf, V, Sc, Co and Ni has a content exceeding the upper limit thereofmentioned above, a wire break is likely to occur since a compoundcontaining the said elements coarsens and deteriorates wire drawingworkability, and also a conductivity tends to decrease. Therefore,ranges of contents of Cu, Ag, Au, Mn, Cr, Zr, Hf, V, Sc, Co and Ni arethe ranges described above, respectively.

The more the contents of Fe, Ti, B, Cu, Ag, Au, Mn, Cr, Zr, Hf, V, Sc,Co and Ni, the lower the conductivity tends to be and the more the wiredrawing workability tends to deteriorate. Therefore, it is preferablethat a sum of the contents of the elements is less than or equal to 2.00mass %. With the aluminum alloy wire rod of the present disclosure,since Fe is an essential element, the sum of contents of Fe, Ti, B, Cu,Ag, Au, Mn, Cr, Zr, Hf, V, Sc, Co and Ni is 0.01 mass % to 2.00 mass %.It is further preferable that the sum of contents of these elements is0.10 mass % to 2.00 mass %. In a case where the above elements are addedalone, the compound containing the element tends to coarsen more as thecontent increases. Since this may degrade wire drawing workability and awire break is likely to occur, ranges of content of the respectiveelements are as specified above.

In order to improve the tensile strength, the elongation, the impactresistance and the bending fatigue resistance while maintaining a highconductivity, the sum of contents of Fe, Ti, B, Cu, Ag, Au, Mn, Cr, Zr,Hf, V, Sc, Co and Ni is particularly preferably 0.10 mass % to 0.80 mass%, and further preferably 0.20 mass % to 0.60 mass %. On the other hand,in order to further improve the tensile strength, the elongation, theimpact resistance and the bending fatigue resistance, although theconductivity will slightly decrease, it is particularly preferably morethan 0.80 mass % to 2.00 mass %, and further preferably 1.00 mass % to2.00 mass %.

<Balance: Al and Incidental Impurities>

The balance, i.e., components other than those described above, includesAl (aluminum) and incidental impurities. Herein, incidental impuritiesmeans impurities contained by an amount which could be containedinevitably during the manufacturing process. Since incidental impuritiescould cause a decrease in conductivity depending on a content thereof,it is preferable to suppress the content of the incidental impurities tosome extent considering the decrease in the conductivity. Componentsthat may be incidental impurities include, for example, Ga, Zn, Bi, andPb.

(2) Dispersion Density of a Mg₂Si Compound Having a Particle Size of 0.5μm to 5.0 μm is Less than or Equal to 3.0×10⁻³ Particles/μm²

The aluminum alloy wire rod of the present disclosure prescribes densityof an Mg₂Si compound having a particular dimension and existing in acrystal grain of an aluminum parent phase. The Mg₂Si compound of 0.5 μmto 5.0 μm is mainly formed in a case where a first heat treatmentdescribed below is performed for two minutes or more and below 480° C.,in a case where a cooling rate of a first heat treatment is less than10° C./s, in a case where a second heat treatment is performed for twominutes or more and below 480° C., and in case where a cooling rate of asecond heat treatment is less than 9° C./s. When Mg₂Si compound of 0.5μm to 5.0 μm is formed with a dispersion density of over 3.0×10⁻³/μm²,an acicular Mg₂Si precipitate formed in the aging heat treatmentdecreases, and a range of improvement of tensile strength, impactresistance, flex fatigue resistance, and conductivity decreases. It ispreferable that the dispersion density of the Mg₂Si compound of 0.5 μmto 5 μm is lower. That is, it is preferable when it is closer to zero.Also, when a density of not only the Mg₂Si compound, but also a compoundcomposed primarily of a Mg—Si system is out of the aforementionedprescribed range, an acicular Mg₂Si precipitate which is formed duringthe aging heat treatment will decrease and a range of improvement oftensile strength, impact resistance, flex fatigue resistance, andconductivity will decrease, a density of a compound composed primarilyof a Mg—Si system is also set similarly in the aforementioned prescribedrange.

(3) Concentration of Each of Si and Mg in a Parent Phase Measured in aSectional Structure is Less than or Equal to 2.00 Mass %

The aluminum alloy wire rod of the present disclosure has, in asectional structure, respective concentrations of Mg and Si other than acompound as described below, and thus ensures strength, elongation andconductivity at levels equivalent to those of a product of the relatedart (aluminum alloy wire disclosed in Japanese Laid-Open PatentPublication No. 2012-229485), and can improve impact resistance and flexfatigue resistance.

It is an essential matter to specify the invention that, in sectionalstructure, each of Mg and Si other than a compound has a concentrationof less than or equal to 2.00 mass %. In a case where at least one ofthe concentrations of Mg and Si is higher than 2.00 mass %, an interfacewith an aluminum parent phase become weak, there is a tendency thattensile strength, elongation, impact resistance and flex fatigueresistance decrease, and also a wire drawing workability may decrease.Further, the concentrations of Mg and Si are preferably less than orequal to 1.50 mass %, respectively, and more preferably, less than orequal to 1.00 mass %, respectively.

Further, according to the present disclosure, it is preferable that, ina sectional structure, a concentration of each of Fe, Ti, B, Cu, Ag, Au,Mn, Cr, Zr, Hf, V, Sc, Co and Ni other than a compound is less than orequal to 1.00 mass %. This is because, in a case where a concentrationof each of the aforementioned added elements exceeds 1.00 mass %, aninterface with an aluminum parent phase weakens, and results in adecrease in a tensile strength, elongation, impact resistance andbending fatigue resistance, and further a decrease in wire drawingproperty.

Further, in a case where, in a sectional structure, a concentration ofeach of Mg, Si, Fe, Ti, B, Cu, Ag, Au, Mn, Cr, Zr, Hf, V, Sc, Co and Niother than a compound is less than or equal to 1.00 mass %, an interfacewith an aluminum parent phase, which is a weak point, decreases, andfurther results in an increase in a tensile strength, elongation, impactresistance, bending fatigue resistance and wire drawing property, andthus it is particularly preferable.

The measurement of concentrations of Mg and Si was performed by usingEDX (Energy Dispersive X-ray Spectroscopy) on a photographic imageobtained by a transmission electron microscope (TEM). A sample having athickness of 0.15 μm was prepared using a Focused Ion Beam (FIB) methodsuch that an area of greater than or equal to 300 μm² is obtained intotal, and a area analysis was carried out to investigate theconcentrations of Mg and Si. In a high concentration part, an areaanalysis or a point analysis with an analysis region of 10 μm² or lesswas carried out to measure the maximum concentrations of added elements.A quantitative analysis was carried out, and in a case where a partexceeding 2.0 mass % was found, a diffraction pattern was observed, andin a case where a diffraction pattern different from that of thealuminum parent phase was obtained, it was determined as a compound andexcluded from a count.

An aluminum alloy wire rod for which an increase in the concentration ofeach of the aforementioned added elements in the parent phase issuppressed can be obtained by controlling performed with a combinationof alloy composition and a manufacturing process. A description is nowmade of a preferred manufacturing method of the aluminum alloy wire rodof the present disclosure.

(Manufacturing Method of the Aluminum Alloy Wire Rod of the PresentDisclosure)

The aluminum alloy wire rod of the present disclosure can bemanufactured with a manufacturing method including sequentiallyperforming each of the processes including [1] melting, [2] casting, [3]hot working (e.g., grooved roller processing), [4] first wire drawing,[5] first heat treatment (solution heat treatment), [6] second wiredrawing, [7] second heat treatment, and [8] aging heat treatment. Notethat a stranding step or a wire resin-coating step may be providedbefore or after the second heat treatment or after the aging heattreatment. Hereinafter, steps of [1] to [8] will be described.

[1] Melting

Melting is performed while adjusting the quantities of each component toobtain an aluminum alloy composition described above.

[2] Casting and [3] Hot Working (e.g., Groove Roller Process)

Subsequently, using a Properzi-type continuous casting rolling millwhich is an assembly of a casting wheel and a belt, molten metal is castwith a water-cooled mold and continuously rolled to obtain a bar havingan appropriate size of, for example, a diameter of 5.0 mmϕ to 13.0 mmϕ.A cooling rate during casting at this time is, in regard to preventingcoarsening of Fe-based crystallized products and preventing a decreasein conductivity due to forced solid solution of Fe, preferably 1° C./sto 20° C./s, but it is not limited thereto. Casting and hot rolling maybe performed by billet casting and an extrusion technique.

[4] First Wire Drawing

Subsequently, the surface is stripped and the bar is made into anappropriate size of, for example, 5.0 mm ϕ to 12.5 mm ϕ, and wiredrawing is performed by cold rolling. It is preferable that a reductionratio η is within a range of 1 to 6. The reduction ratio η isrepresented by:η=ln(A0/A1),

where A0 is a wire rod cross sectional area before wire drawing and A1is a wire rod cross sectional area after wire drawing.

In a case where the reduction ratio η is less than 1, in a heatprocessing of a subsequent step, a recrystallized particle coarsens anda tensile strength and an elongation significantly decreases, which maycause a wire break. In a case where the reduction ratio η is greaterthan 6, the wire drawing becomes difficult and may be problematic from aquality point of view since a wire break might occur during a wiredrawing process. The stripping of the surface has an effect of cleaningthe surface, but does not need to be performed.

[5] First Heat Treatment (Solution Heat Treatment)

A first heat treatment is applied on the cold-drawn work piece. Thefirst heat treatment of the present disclosure is a solution heattreatment that is performed for a purpose such as dissolving compound ofMg and Si randomly contained in the work piece into a parent phase of analuminum alloy. The solution heat treatment is performed immediatelybefore the aging heat treatment in the related art. Whereas, in thepresent disclosure, it is performed before the second wiredrawing.Accordingly, it is possible to homogenize Mg and Si during a working andleads to a suppression in the segregation of a Mg component and a Sicomponent at grain boundaries after the final aging heat treatment. Thatis, the first heat treatment of the present disclosure is a heattreatment which is different from an intermediate heat treatment whichis usually performed during the wire drawing in a manufacturing methodof the related art. The first heat treatment is specifically a heattreatment including heating to a predetermined temperature in a range of480° C. to 620° C. and thereafter cooling at an average cooling rate ofgreater than or equal to 10° C./s to a temperature of at least to 150°C. When a predetermined temperature during the first heat treatmenttemperature is higher than 620° C., an aluminum alloy wire containingthe added elements will partly melt, and there is a possibility of adecrease in elongation, impact resistance and bending fatigueresistance, and when the predetermined temperature is lower than 480°C., the solution treatment cannot be achieve sufficiently and anincreasing effect of the tensile strength in the subsequent aging heattreatment step cannot be obtained sufficiently, and the tensile strengthwill decrease. Therefore, the predetermined temperature during theheating in the first heat treatment is in a range of 480° C. to 620° C.and preferably in a range of 500° C. to 600° C., and more preferably ina range of 520° C. to 580° C.

A method of performing the first heat treatment may be, for example,batch heat treatment or may be continuous heat treatment such ashigh-frequency heating, conduction heating, and running heating.

In a case where high-frequency heating and conduction heating are used,a wire rod temperature increases with a passage of time, since itnormally has a structure in which electric current continues flowingthrough the wire rod. Accordingly, since the wire rod may melt when anelectric current continues flowing through, it is necessary to performheat treatment in an appropriate time range. In a case where runningheating is used, since it is an annealing in a short time, thetemperature of a running annealing furnace is usually set higher thanthe wire rod temperature. Since the wire rod may melt with a heattreatment over a long time, it is necessary to perform heat treatment inan appropriate time range. Also, all heat treatments require at least apredetermined time period in which Mg and Si compounds containedrandomly in the work piece will be dissolved into an aluminum parentphase. Hereinafter, the heat treatment by each method will be described.

The continuous heat treatment by high-frequency heating is a heattreatment by joule heat generated from the wire rod itself by an inducedcurrent by the wire rod continuously passing through a magnetic fieldcaused by a high frequency. Steps of rapid heating and rapid cooling areincluded, and the wire rod can be heat-treated by controlling the wirerod temperature and the heat treatment time. The cooling is performedafter rapid heating by continuously allowing the wire rod to passthrough water or in a nitrogen gas atmosphere. This heat treatment timeis 0.01 s to 2 s, preferably 0.05 s to 1 s, and more preferably 0.05 sto 0.5 s.

The continuous conducting heat treatment is a heat treatment by jouleheat generated from the wire rod itself by allowing an electric currentto flow in the wire rod that continuously passes two electrode wheels.Steps of rapid heating and rapid cooling are included, and the wire rodcan be heat-treated by controlling the wire rod temperature and the heattreatment time. The cooling is performed after rapid heating bycontinuously allowing the wire rod to pass through water, atmosphere ora nitrogen gas atmosphere. This heat treatment time period is 0.01 s to2 s, preferably 0.05 s to 1 s, and more preferably 0.05 s to 0.5 s.

A continuous running heat treatment is a heat treatment in which thewire rod continuously passes through a heat treatment furnace maintainedat a high-temperature. Steps of rapid heating and rapid cooling areincluded, and the wire rod can be heat-treated by controlling thetemperature in the heat treatment furnace and the heat treatment time.The cooling is performed after rapid heating by continuously allowingthe wire rod to pass through water, atmosphere or a nitrogen gasatmosphere. This heat treatment time period is 0.5 s to 120 s,preferably 0.5 s to 60 s, and more preferably 0.5 s to 20 s.

The batch heat treatment is a method in which a wire rod is placed in anannealing furnace and heat-treated at a predetermined temperaturesetting and a setup time. The wire rod itself should be heated at apredetermined temperature for about several tens of seconds, but inindustrial application, it is preferable to perform for more than 30minutes to suppress uneven heat treatment on the wire rod. An upperlimit of the heat treatment time is not particularly limited as long asthere are five crystal grains when counted in a radial direction of awire rod, but in industrial application, since productivity increaseswhen performed in a short time, heat treatment is performed within tenhours, and preferably within six hours.

In a case where one or both of the wire rod temperature or the heattreatment time are lower than conditions defined above, a solutionprocess will be incomplete and an amount of an Mg₂Si precipitateproduced in the aging heat treatment, which is a post-process,decreases. Thus, a range of improvement of tensile strength, impactresistance, flex fatigue resistance and conductivity decreases. In acase where one or both of the wire rod temperature and the annealingtime are higher than conditions defined above, coarsening of crystalgrains and also a partial fusion (eutectic fusion) of a compound phasein the aluminum alloy wire rod occur. Thus, the tensile strength and theelongation decrease, and a wire break is likely to occur when handlingthe wire rod.

It is an essential matter to specify the invention to perform thecooling in the first heat treatment at an average cooling rate ofgreater than or equal to 10° C./s to a temperature of at least 150° C.This is because, at an average cooling rate of less than 10° C./s,precipitates of Mg and Si or the like will be produced during thecooling and a solution process will not be performed sufficiently, andthus an improvement effect of the tensile strength in the subsequentaging heat treatment step will be restricted and a sufficient tensilestrength will not be obtained. Note that the average cooling rate ispreferably greater than or equal to 50° C./s, and more preferablygreater than or equal to 100° C./s.

For any of the heat treatment methods described above, the cooling inthe first heat treatment of the present disclosure is preferablyperformed by heating the aluminum alloy wire rod after the first wiredrawing to a predetermined temperature and thereafter allowing the wirerod to pass through water, but in such a case, the cooling rate ispossible cannot be measured accurately. Thus, in such a case, in each ofthe heat treatment methods, assuming that an aluminum alloy wire rod iscooled to water temperature (approximately 20° C.) immediately afterwater cooling, a cooling rate calculated as described below was taken asan average cooling rate by water cooling after heating for each of theheat treatment methods. That is, in a batch heat treatment, from theperspective that it is important that a period of time in which 150° C.or above is maintained is within 40 seconds from the beginning of thecooling, the cooling rate is greater than or equal to (500−150)/40=8.75°C./s when it is heat-treated to 500° C., and greater than or equal to(600−150)/40=11.25° C./s when it is heat-treated to 600° C. In acontinuous heat treatment by high-frequency heating, the cooling rate is100° C./s or above, since it is a mechanism that, after heating, passesan aluminum alloy wire rod for a few to several meters at a wire speedof 100 m/min to 1500 m/min and thereafter water cools the aluminum alloywire rod. In a continuous heat treatment by conduction heating, thecooling rate is 100° C./s or above, since it is a mechanism that,immediately after heating, water cools an aluminum alloy wire rod. In acontinuous heat treatment by running heating, the cooling rate is 100°C./s or above, in a case of a mechanism that, immediately after heating,water cools an aluminum alloy wire rod at a wire speed of 10 m/min to500 m/min, and in a case of a mechanism that, after heating, air coolswhile being passed for a few to several meters to a few to several tensof meters, assuming that the aluminum alloy wire rod is cooled to roomtemperature (approximately 20° C.) immediately after being wound up on adrum with a length of section during air-cooling being 10 m and acooling start temperature being 500° C., it can be calculated that acooling of approximately 6° C./s to 292° C./s is carried out. Thus, thecooling rate of 10° C./s or above is well possible. However, in any ofthe heat treatment methods, it is only necessary to rapidly cool to atleast 150° C. from the perspective of achieving a purpose of solutionheat treatment.

Further, it is preferable that the cooling in the first heat treatmentis performed at an average cooling rate of 20° C./s or above to atemperature of at least 250° C. to give an effect of improving thetensile strength in the subsequent aging heat treatment step bysuppressing the precipitation of Mg and Si. Since peaks of precipitationtemperature zones of Mg and Si are located at 300° C. to 400° C., it ispreferable to speed up the cooling rate at least at the said temperatureto suppress the precipitation of Mg and Si during the cooling.

[6] Second Wire Drawing

After the first heat treatment, wire drawing is further carried out in acold processing. During this, a reduction ratio η is preferably within arange of 1 to 6. The reduction ratio η has an influence on formation andgrowth of recrystallized grains. This is because, if the reduction ratioη is less than 1, during the heat treatment in a subsequent step, thereis a tendency that coarsening of recrystallized grains occur and thetensile strength and the elongation drastically decrease, and if thereduction ratio η is greater than 6, wire drawing becomes difficult andthere is a tendency that problems arise in quality, such as a wire breakduring wire drawing.

[7] Second Heat Treatment

A second heat treatment is performed on a cold wire-drawn work piece.The second heat treatment is a heat treatment which is different fromthe first heat treatment described above and the aging heat treatmentdescribed below. The second heat treatment may be performed by batchannealing similarly to the first heat treatment, or may be performed bycontinuous annealing such as high-frequency heating, conduction heating,and running heating. However, it is necessary to perform in a shorttime. This is because when heat treatment is applied for a long time,precipitation of Mg and Si occurs, and an effect of improving of thetensile strength in the subsequent aging heat treatment step cannot beobtained and the tensile strength decreases. That is, the second heattreatment needs to be applied by a manufacturing method that can performprocesses of increasing the temperature from 150° C., holding,decreasing the temperature to 150° C. in less than two minutes.Therefore, in the case of the batch annealing that is usually carriedout by a holding for a long period of time, it is difficult topractically perform, and thus continuous annealing such ashigh-frequency heating, conduction heating, and running heating ispreferable.

The second heat treatment is not a solution heat treatment such as thefirst heat treatment, but rather a heat treatment that performed forrecovering a flexibility of the wire rod, and to improve elongation. Theheating temperature of the second heat treatment is higher than or equalto 300° C. and lower than 480° C. This is because when heatingtemperature of the second heat treatment is lower than 300° C.,recrystallization will not take place, and there is a tendency that aneffect of improving the elongation cannot be obtained, and when theheating temperature is 480° C. or higher, a part in which aconcentration of Mg or Si is high is likely to occur inside grains or atgrain boundaries in the parent phase, and a tensile strength, anelongation, an impact resistance, and a flex fatigue resistance tend todecrease. Further, the heating temperature of the second heat treatmentis preferably 300° C. to 450° C., and more preferably 325° C. to 450° C.The heating time of the second heat treatment is shorter than twominutes, since if it is two minutes or longer, an Mg₂Si compound of 0.5μm to 5.0 μm is likely to be produced and a dispersion density of theMg₂Si compound of 0.5 μm to 5.0 μm tends to exceed 3.0×10⁻³/μm².

It is an essential matter to specify the invention to perform thecooling in the second heat treatment at an average cooling rate ofgreater than or equal to 8° C./s to a temperature of at least 150° C.This is because, at an average cooling rate of less than 9° C./s,precipitates such as Mg and Si will be produced during the cooling, andthis restricts an effect of improving the tensile strength by thesubsequent aging heat treatment step and a sufficient tensile strengthwill not be obtained. Note that the average cooling rate is preferablygreater than or equal to 50° C./s, and more preferably greater than orequal to 100° C./s.

Further, in the cooling in the second heat treatment, it is preferableto perform at an average cooling rate of greater than or equal to 20°C./s to a temperature of at least 250° C., to give an effect ofimproving the tensile strength by a subsequent aging heat treatment stepby suppressing the precipitation of Mg and Si. Since the peaks ofprecipitation temperature zones of Mg and Si are located at 300° C. to400° C., it is preferable to speed up the cooling rate at least at thesaid temperature to suppress the precipitation of Mg and Si.

[8] Aging Heat Treatment

Subsequently, an aging heat treatment is applied. The aging heattreatment is conducted to cause precipitation of acicular Mg₂Siprecipitates. The heating temperature in the aging heat treatment ispreferably 140° C. to 250° C. When the heating temperature is lower than140° C., it is not possible to cause precipitation of the acicular Mg₂Siprecipitates sufficiently, and strength, impact resistance, bendingfatigue resistance and conductivity tend to lack. When the heatingtemperature is higher than 250° C., due to an increase in the size ofthe Mg₂Si precipitate, the conductivity increases, but strength, impactresistance, and bending fatigue resistance tend to lack. The heatingtemperature in the aging heat treatment is, preferably 160° C. to 200°C. when an impact resistance and a high flex fatigue resistance are ofimportance, and preferably 180° C. to 220° C. when conductivity is ofimportance. As for the heating time, the most suitable length of timevaries with temperature. In order to improve a strength, an impactresistance, and a bending fatigue resistance, the heating time ispreferably a long when the temperature is low and the heating time isshort when the temperature is high. Considering the productivity, ashort period of time is preferable, which is preferably 15 hours or lessand further preferably 10 hours or less. It is preferable that, thecooling in the aging heat treatment is performed at the fastest possiblecooling rate to prevent variation in characteristics. However, in a casewhere it cannot be cooled fast in a manufacturing process, an agingcondition can be set appropriately by taking into account that anincrease and a decrease in the acicular Mg₂Si precipitate may occurduring the cooling.

A strand diameter of the aluminum alloy wire rod of the presentdisclosure is not particularly limited and can be determined asappropriate depending on an application, and it is preferably 0.1 mmϕ to0.5 mmϕ for a fine wire, and 0.8 mmϕ to 1.5 mmϕ for a case of a middlesized wire. The present aluminum alloy wire rod has an advantage in thatit can be used as a thin single wire as an aluminum alloy wire, but mayalso be used as an aluminum alloy stranded wire obtained by stranding aplurality of them together, and among the aforementioned steps [1] to[8] of the manufacturing method of the present disclosure, afterbundling and stranding a plurality of aluminum alloy wires obtained bysequentially performing each of steps [1] to [6], the steps of [7]second heat treatment and [8] aging heat treatment may be performed.

Also, in the present disclosure, homogenizing heat treatment performedin the prior art may be performed as a further additional step after thecontinuous casting rolling. Since a homogenizing heat treatment canuniformly disperse precipitates (mainly Mg—Si based compound) of theadded element, it becomes easy to obtain a uniform crystal structure inthe subsequent first heat treatment, and as a result, improvement in atensile strength, an elongation, an impact resistance, and a flexfatigue resistance can be obtained more stably. The homogenizing heattreatment is preferably performed at a heating temperature of 450° C. to600° C. and a heating time of 1 to 10 hours, and more preferably 500° C.to 600° C. Also, as for the cooling in the homogenizing heat treatment,a slow cooling at an average cooling rate of 0.1° C./min to 10° C./minis preferable since it becomes easier to obtain a uniform compound.

Note that the above description merely indicates an example of anembodiment of the present disclosure and can add various modificationmay be added to the claims. For example, the aluminum alloy wire rod ofthe present disclosure has an impact absorption energy of greater thanor equal to 5 J/mm², and can achieve an improved impact resistance.Further, a number of cycles to fracture measured by a flex fatigue testis 200,000 times or more, and can achieve an improved flex fatigueresistance. Also, the aluminum alloy wire rod of the present disclosurecan be used as an aluminum alloy wire, or as an aluminum alloy strandedwire obtained by stranding a plurality of aluminum alloy wires, and mayalso be used as a coated wire having a coating layer at an outerperiphery of the aluminum alloy wire or the aluminum alloy strandedwire, and, in addition, it can also be used as a wire harness having acoated wire and a terminal fitted at an end portion of the coated wire,the coating layer being removed from the end portion.

EXAMPLE

The present disclosure will be described in detail based on thefollowing examples. Note that the present disclosure is not limited toexamples described below.

Examples and Comparative Examples

Using a Properzi-type continuous casting rolling mill, molten metalcontaining Mg, Si, Fe and Al, and selectively added Ti, B, Cu, Ag, Au,Mn, Cr, Zr, Hf, V, Sc, Co and Ni, with contents (mass %) shown in Tables1-1, 1-2, 1-3 and 2 is cast with a water-cooled mold and rolled into abar of approximately 9.5 mmϕ. A casting cooling rate at this time wasapproximately 15° C./s. Then, a first wire drawing was carried out toobtain a predetermined reduction ratio. Then, an first heat treatmentwas performed with conditions indicated in Tables 3-1, 3-2, 3-3, 4-1 and4-2 on a work piece subjected to the first wire drawing, and further, asecond wire drawing was performed until a wire size of 0.31 mmϕ wasobtained. Then, a second heat treatment was applied under conditionsshown in Tables 3-1, 3-2, 3-3, 4-1 and 4-2. In both of the first andsecond heat treatments, in a case of a batch heat treatment, a wire rodtemperature was measured with a thermocouple wound around the wire rod.In a case of continuous conducting heat treatment, since measurement ata part where the temperature of the wire rod is the highest is difficultdue to the facility, the temperature was measured with a fiber opticradiation thermometer (manufactured by Japan Sensor Corporation) at aposition upstream of a portion where the temperature of the wire rodbecomes highest, and a maximum temperature was calculated inconsideration of joule heat and heat dissipation. In a case ofhigh-frequency heating and consecutive running heat treatment, a wirerod temperature in the vicinity of a heat treatment section outlet wasmeasured. After the second heat treatment, an aging heat treatment wasapplied under conditions shown in Tables 3-1, 3-2, 3-3, 4-1 and 4-2 toproduce an aluminum alloy wire. Note that Comparative Example 12 wasalso evaluated since it has a composition of sample No. 2 in Table 1 inPatent Japanese Laid-Open Patent Publication No. 2012-229485 and analuminum alloy wire was produced with a manufacturing method equivalentto the manufacturing method disclosed in Japanese Laid-Open PatentPublication No. 2012-229485.

For each of aluminum alloy wires of the Example and the ComparativeExample, each characteristic was measured by methods shown below. Theresults are shown in Tables 3-1, 3-2, 3-3, 4-1, 4-2 and 5.

(A) Observation and Evaluation Method of Dispersion Density of Mg₂SiCompound Particles

Wire rods of Examples and Comparative Examples were formed as thin filmsby a Focused Ion Beam (FIB) method and an arbitrary range was observedusing a transmission electron microscope (TEM). The Mg₂Si compound wassubjected to a composition analysis by EDX and the kinds of compoundswere identified. Further, since the Mg₂Si compound was observed as aplate-like compound, a compound with a part corresponding to an edge ofthe plate-like compound is 0.5 μm to 5.0 μm was counted in the capturedimage. In a case where a compound extends outside the measuring range,it is counted into the number of compound if 0.5 μm or more of thecompound was observed. The dispersion density of the Mg₂Si compound wasobtained by setting a range in which 20 or more can be counted andcalculating using an equation: Mg₂Si Dispersion Density of Compound(number/μm²)=Number of Mg₂Si Compounds (number)/Count Target Range(μm²). Depending on the situation, a plurality of photographic imageswere used as the count target range. In a case where there were not muchcompound and it was not possible to count 20 or more, 1000 μm² wasspecified and a dispersion density in that range was calculated.

Note that the dispersion density of an Mg₂Si compound was calculatedwith a sample thickness of the thin film of 0.15 am being taken as areference thickness. In a case where the sample thickness is differentfrom the reference thickness, the dispersion density of the Mg₂Sicompound of a reference thickness can be calculated by converting thesample thickness with the reference thickness, in other words,multiplying (reference thickness/sample thickness) by a dispersiondensity of the Mg₂Si compound of the sample thickness calculated basedon the captured image. In the present examples and the comparativeexamples, all the samples were produced using a FIB method by settingthe sample thickness to approximately 0.15 μm. If the dispersion densityof the Mg₂Si compound was within a range of 0 to 3.0×10⁻³ μm², it wasdetermined that the dispersion density of the Mg₂Si compound is withinan appropriate range and indicated as “A”, and if it was not within arange of 0 to 3.0×10⁻³ μm², it was determined that the dispersiondensity of the Mg₂Si compound is within an inappropriate range andindicated as “B”.

(B) Measurement of Concentrations of Mg and Si in Parent Phase

The measurement of concentrations of Mg and Si in a parent phase wasperformed by using EDX (Energy Dispersive X-ray Spectroscopy) on aphotographic image obtained by a transmission electron microscope (TEM).A sample having a thickness of 0.15 μm was prepared using a Focused IonBeam (FIB) method such that an area of greater than or equal to 300 μm²is obtained in total, and an area analysis was carried out toinvestigate the concentrations of Mg and Si. In a high concentrationpart, an area analysis or a point analysis with an analysis region of 10μm² or less was carried out to measure the maximum concentrations ofadded elements. A quantitative analysis was carried out, and in a casewhere a portion exceeding 2.0 mass % was found, a diffraction patternwas observed, and in a case where a diffraction pattern different fromthat of the aluminum parent phase was obtained, it was determined as acompound and excluded from a count. In Tables 3-1 to 4-2, in a casewhere the concentration of each of Mg, Si, Fe, Ti, B, Cu, Ag, Au, Mn,Cr, Zr, Hf, V, Sc, Co and Ni in a parent phase is less than or equal to1.00 mass % at each analysis region, it was indicated as “A”; in a casewhere the concentration of at least one of Mg and Si in a parent phaseis greater than 1.00 mass % and less than or equal to 2.00 mass % andalso the concentration of each of Fe, Ti, B, Cu, Ag, Au, Mn, Cr, Zr, Hf,V, Sc, Co and Ni in a parent phase is less than or equal to 1.00 mass %at each analysis region, it was indicated as “B”; in a case where theconcentration of each of Mg and Si in a parent phase was less than orequal to 2.00 mass % and also the concentration of Fe, Ti, B, Cu, Ag,Au, Mn, Cr, Zr, Hf, V, Sc, Co and Ni is greater than 1.00 mass % at eachanalysis region, it was indicated as “C”; and in a case where theconcentration of at least one of Mg and Si in a parent phase was greaterthan 2.00 mass % at any one of the analysis regions, it was evaluated asa being failed and indicated as “D”.

(C) Measurement of Tensile Strength (TS) and Flexibility (Elongationafter Fracture)

In conformity with JIS Z2241, a tensile test was carried out for threematerials under test (aluminum alloy wires) each time, and an averagevalue thereof was obtained. The tensile strength of greater than orequal to 150 MPa was regarded as a pass level so as to keep the tensilestrength of a crimp portion at a connection portion between an electricwire and a terminal and to withstand a load abruptly applied during aninstallation work to a car body. As for the elongation, greater than orequal to 5% was regarded as a pass.

(D) Conductivity (EC)

In a constant temperature bath in which a test piece of 300 mm in lengthis held at 20° C. (±0.5° C.), a resistivity was measured for threematerials under test (aluminum alloy wires) each time using a fourterminal method, and an average conductivity was calculated. Thedistance between the terminals was 200 mm. The conductivity is notparticularly prescribed, but those greater than or equal to 40% IACS wasregarded as a pass.

(E) Impact Absorption Energy

It is an index showing how much impact the aluminum alloy wire rod canwithstand which is calculated by (potential energy of weight)/(crosssectional area of aluminum alloy wire rod) immediately before a wirebreak of the aluminum alloy wire rod. Specifically, a weight wasattached to one end of the aluminum alloy wire rod wire and the weightwas allowed to fall freely from a height of 300 mm. The weight waschanged into a heavier weight sequentially, and the impact absorptionenergy was calculated from the weight immediately before a wire break.It can be said that the larger the impact absorption energy is, thehigher the impact absorption. As for the impact absorption energy, 5J/cm² or higher was regarded as a pass level.

(F) Number of Cycles to Fracture

As a reference of the bending fatigue resistance, a strain amplitude atan ordinary temperature is assumed as ±0.17%. The bending fatigueresistance varies depending on the strain amplitude. In a case where thestrain amplitude is large, a fatigue life decreases, and in a case wherethe strain amplitude is small, the fatigue life increases. Since thestrain amplitude can be determined by a wire size of the wire rod and aradius of curvature of a bending jig, a bending fatigue test can becarried out with the wire size of the wire rod and the radius ofcurvature of the bending jig being set arbitrarily. With a reversedbending fatigue tester manufactured by Fujii Seiki Co., Ltd. (existingcompany Fujii Co., Ltd.) and using a jig that can give a 0.17% bendingstrain, a repeated bending was carried out and a number of cycles tofracture was measured. In the present disclosure, number of cycles tofracture of 200,000 times or more was regarded as a pass.

(G) Number of Cycles to Fracture in a High Temperature Environment

The reversed bending fatigue tester described above was placed in aconstant temperature tank at a temperature of 120° C., and a bendingfatigue test was carried out on the aluminum alloy wire rods of SampleNos. 4, 5, 6, 8, 9, 10, 13, 18 and 20 indicated in Table 1. As areference of the bending fatigue resistance, a strain amplitude in ahigh temperature environment is assumed as ±0.17%.

TABLE 1-1 COMPOSITION (MASS %) No. Mg Si Fe Au Ag Cu Cr Mn Zr Ti B Hf VSc Co Ni Al EXAMPLE 1 0.34 0.34 0.20 — — — — — — 0.010 0.003 — — — — —BALANCE 2 0.45 0.51 0.20 — — 0.20 — — — 0.010 0.003 — — — — — 3 0.640.64 0.20 — — — 0.20 — — 0.010 0.003 — — — — — 4 0.64 0.47 0.10 — — — —0.20 — 0.010 0.003 — — — — — 5 0.55 0.55 0.20 — — — — — 0.10 0.010 0.003— — — — — 6 0.77 0.57 0.02 — — 0.10 0.10 — — 0.010 0.003 — — — — — 70.34 0.39 0.20 — — 0.10 — 0.40 — 0.010 0.006 — — — — — 8 0.77 0.88 0.20— — 0.05 — — 0.20 0.010 0.003 — — — — — 9 0.55 0.41 0.20 — — — 0.10 0.10— 0.005 0.003 — — — — — 10 0.55 0.63 0.40 — — — 0.40 — 0.05 0.010 0.003— — — — — 11 0.77 0.77 0.20 — — — — 0.20 0.10 0.010 0.003 — — — — — 120.34 0.39 0.20 — — 0.05 0.05 0.40 — 0.010 0.003 — — — — — 13 0.45 0.330.80 — — — 0.10 0.05 0.20 0.020 0.003 — — — — — 14 0.55 0.63 0.20 — —0.20 — 0.10 0.20 0.010 0.006 — — — — — 15 0.64 0.73 0.20 — — 0.10 0.10 —0.10 0.010 0.003 — — — — — 16 0.34 0.39 0.20 — — — 0.10 — — — — — — — —— 17 0.45 0.45 0.20 — — — — 0.20 — — — — — — — — 18 0.64 0.47 0.20 0.50— — — — 0.10 0.010 0.003 — — — — — 19 0.64 0.47 0.20 0.11 — — — 0.20 —0.010 0.012 — — — — — 20 0.64 0.47 0.20 — 0.10 — — — 0.10 0.010 0.003 —— — — — N.B. NUMERICAL VALUES IN BOLD ITALIC IN THE TABLE ARE OUT OFAPPROPRIATE RANGE OF THE EXAMPLE

TABLE 1-2 COMPOSITION (MASS %) No. Mg Si Fe Au Ag Cu Cr Mn Zr Ti B Hf VSc Co Ni Al EXAMPLE 21 0.64 0.47 0.20 — 0.20 — 0.20 — — 0.010 0.003 — —— — — BALANCE 22 0.50 0.50 0.30 — — 0.30 0.10 0.10 0.20 0.010 0.003 — —— — — 23 0.50 0.50 0.30 0.10 — 0.90 — — — 0.010 0.003 — — — — — 24 0.500.50 0.01 — 0.20 0.60 0.40 0.30 — 0.010 0.003 — — — — — 25 0.50 0.500.20 — — — 0.20 0.80 0.20 0.010 0.003 — — — — — 26 0.50 0.50 0.20 — — —0.80 — 0.50 0.010 0.003 — — — — — 27 0.64 0.47 0.20 — — — — — — 0.0050.001 0.10 — — — — 28 0.55 0.63 0.20 — — — — — — 0.010 — 0.01 0.01 — — —29 0.45 0.51 0.20 — — — — — — 0.003 — — 0.10 — — — 30 0.91 0.98 0.20 — —— — 0.05 — 0.020 0.005 — — — — — 31 0.33 0.33 0.20 — — 0.03 — — — 0.0100.001 — — — — — 32 0.45 0.33 0.20 — — 0.40 — — — 0.010 0.001 — — — — —33 0.34 0.39 0.10 — — — — — — 0.010 0.003 — — — 0.05 — 34 0.34 0.39 0.10— — — — — — — — — — — — — 35 0.34 0.39 0.10 — — — — — — — — — — — — — 360.50 0.50 0.20 — — — — — — 0.010 0.003 0.50 — — — — 37 0.50 0.50 0.20 —— — — — — 0.010 0.003 0.01 0.01 — — — 38 0.50 0.50 0.20 — — — — — —0.010 0.003 — — 0.10 — — 39 0.50 0.50 0.20 — — — — — — 0.010 0.003 — — —— 0.10 40 0.50 0.50 0.20 — — — — — — 0.010 0.003 — — 0.10 — 0.10 N.B.NUMERICAL VALUES IN BOLD ITALIC IN THE TABLE ARE OUT OF APPROPRIATERANGE OF THE EXAMPLE

TABLE 1-3 COMPOSITION (MASS %) No. Mg Si Fe Au Ag Cu Cr Mn Zr Ti B Hf VSc Co Ni Al EXAMPLE 41 0.64 0.47 0.20 — — — — — — 0.010 0.003 — 0.100.20 — — BALANCE 42 0.64 0.47 0.20 — — — — — — 0.010 0.003 0.10 0.20 — —— 43 0.64 0.47 0.20 — — — — — — 0.010 0.003 0.20 — — — 0.10 44 0.64 0.470.20 — — — — — — 0.010 0.003 — — 0.01 — 0.01 45 0.64 0.47 0.20 — — — — —— 0.010 0.003 — 0.01 — 0.20 0.50 46 0.55 0.63 0.20 — — 0.20 — — — 0.0100.003 — — 0.10 — — 47 0.55 0.63 0.20 — — 0.20 — 0.10 — 0.010 0.003 — —0.10 — — 48 0.55 0.63 0.20 — — 0.20 0.05 0.05 — 0.010 0.003 — — — 0.100.10 49 0.55 0.63 0.20 — — — — — — 0.010 0.003 — — — — — 50 0.55 0.630.20 — — — 0.25 — — 0.010 0.003 — — — — 0.10 51 0.50 0.50 0.20 — — — —0.20 — 0.010 0.003 — — — — 0.10 52 0.50 0.50 0.20 — — — — — — 0.0100.003 — — 0.40 — — 53 0.50 0.50 0.20 — — — — — 0.10 0.010 0.003 — 0.44 —— — 54 0.64 0.73 1.00 — — — — 0.10 — 0.010 0.003 — — — — — 55 0.64 0.731.20 — — — — — — 0.010 0.003 — — — — — 56 0.64 0.73 1.40 — — — — — 0.100.010 0.003 — — — — — 57 1.00 1.00 0.20 — — — 0.10 — — 0.010 0.003 — — —— — N.B. NUMERICAL VALUES IN BOLD ITALIC IN THE TABLE ARE OUT OFAPPROPRIATE RANGE OF THE EXAMPLE

TABLE 2 COMPOSITION (MASS%) No. Mg Si Fe Au Ag Cu Cr Mn Zr Ti B Hf V ScCo Ni Al COM-  1

0.39 0.20 — — — — — — 0.010 0.003 — — — — — BALANCE PAR-  2

0.39 0.20 — — — — — — 0.010 0.003 — — — — — ATIVE  3 0.55

0.20 — — — — 0.20 — 0.010 0.003 — — — — — EX-  4 0.55

0.20 — — — — 0.20 — 0.010 0.003 — — — — — AM-  5 0.55 0.55

— — — — — — 0.010 0.003 — — — — — PLE  6 0.55 0.55 0.20

— — — — — 0.010 0.003 — —

— —  7 0.55 0.55 0.20 — — — —

— 0.010 0.003 — — — — —  8 0.55 0.55 0.20 — — —

— — 0.010 0.003 — — — — —  9 0.55 0.55 0.20 — — — — —

0.010 0.003 —

— — — 10 0.55 0.55 0.20 — — — — — —

— — — — — 11

0.21 — — — — — — 0.010 0.003 — — — — — 12 0.88 0.64 0.13 — — — — 0.20 —0.020 0.004 — — — — — 13 0.51 0.11 0.15 — — — — — 0.07 0.010 0.002 — — —— — 14 0.67 0.55 0.14 — — — — — — 0.020 0.004 — — — — — 15 0.62 0.520.14 — — — — 0.21 — 0.020 0.004 — — — — — 16 0.45 0.51 0.20 — — — — —0.20 0.020 0.005 — — — — — 17 0.45 0.51 0.20 — — — — 0.20 — 0.020 0.005— — — — — 18 0.45 0.51 0.20 — — 0.10 0.20 — — 0.020 0.005 — — — — — 190.45 0.51 0.20 — 0.20 — — — — 0.020 0.005 — — — — — N.B. NUMERAL VALUESIN BOLD ITALIC IN THE TABLE ARE OUT OF APPROPRIATE RANGE OF THE EXAMPLE

TABLE 3-1 AGING HEAT 1ST HEAT TREATMENT CONDITION SECOND HEAT TREATMENTCONDITION TREATMENT HEAT HEATING COOLING RATE HEAT HEATING COOLING RATECONDITION TREATMENT TEMP. HEATING TO AT LEAST TREATMENT TEMP HEATING TOAT LEAST TEMP. TIME No. METHOD (° C.) TIME 150° C. (° C./s) METHOD (°C.) TIME 150° C. (° C./s) (° C.) (HOUR) EXAMPLE 1 BATCH 520 1 h 30HIGH-FREQ. 450 0.18 s >=100 160 5 2 HIGH-FREQ. 550 0.18 s >=100HIGH-FREQ. 450 0.18 s >=100 180 5 3 HIGH-FREQ. 600 0.09 s >=100HIGH-FREQ. 450 0.09 s >=100 200 5 4 HIGH-FREQ. 550 0.18 s >=100HIGH-FREQ. 475 0.18 s >=100 200 10 5 HIGH-FREQ. 520 0.72 s >=100HIGH-FREQ. 475 0.36 s >=100 180 10 6 CONDUCTION 550 0.24 s >=100CONDUCTION 450 0.24 s >=100 160 10 7 CONDUCTION 520 0.96 s >=100CONDUCTION 400 0.96 s >=100 140 15 8 CONDUCTION 550 0.48 s >=100CONDUCTION 450 0.48 s >=100 180 15 9 CONDUCTION 600 0.06 s >=100CONDUCTION 475 0.06 s >=100 180 15 10 RUNNING 550 4.8 s 70 RUNNING 400 4.8 s 70 200 1 11 RUNNING 600 3.2 s >=100 RUNNING 450  3.2 s >=100 2205 12 BATCH 520 3 h 20 CONDUCTION 400 0.48 s >=100 180 10 13 BATCH 550 3h 30 CONDUCTION 400 0.48 s >=100 160 10 14 BATCH 600 3 h 30 CONDUCTION475 0.24 s >=100 160 15 15 CONDUCTION 580 0.12 s >=100 CONDUCTION 4750.12 s >=100 160 5 16 HIGH-FREQ. 550 0.18 s >=100 HIGH-FREQ. 400 0.36s >=100 180 1 17 HIGH-FREQ. 520 0.36 s >=100 HIGH-FREQ. 400 0.36 s >=100160 1 18 BATCH 550 5 h 20 HIGH-FREQ. 450 0.72 s >=100 200 5 19 BATCH 5201 h 20 HIGH-FREQ. 450 0.72 s >=100 140 10 20 BATCH 550 1 h 15 CONDUCTION400 0.48 s >=100 180 5 REFERENCE LEVEL OF DISTRIBUTION PERFORMANCEVALUATION CONCENTRATION OF DENSITY OF NUMBER ADDED ELEMENTS IN Mg₂Si OFCYCLES PART OTHER THAN COMPOUND OF ELONGATION IMPACT TO COMPOUND INPARTICLE SIZE TENSILE AFTER ABSORBING FRACTURE SECTIONAL 0.5-5.0 mmSTRENGTH FRACTURE CONDUCTIVITY ENERGY (×10⁴ No. STRUCTURE(PARTICLES/μm²) (MPa) (%) (% IACS) (J/mm²) CYCLES) EXAMPLE 1 C A 150 1454 7 23 2 B A 250 13 53 18 104 3 C A 288 8 45 14 162 4 B A 255 13 46 19132 5 C A 315 8 52 16 141 6 B A 330 9 46 19 164 7 C A 155 19 44 11 60 8B A 365 7 48 17 200 9 C A 250 13 48 18 96 10 C A 280 11 44 19 146 11 C A300 9 43 17 184 12 C A 195 12 48 11 60 13 C A 170 12 47 8 57 14 C A 32013 46 27 148 15 B A 322 9 44 19 176 16 B A 155 17 50 10 60 17 B A 180 1546 12 82 18 C A 265 11 50 16 132 19 C A 265 16 41 25 132 20 C A 300 1451 26 132 N.B. NUMERICAL VALUES IN BOLD ITALIC IN THE TABLE ARE OUT OFAPPROPRIATE RANGE OF THE EXAMPLE

TABLE 3-2 AGING HEAT 1ST HEAT TREATMENT CONDITION SECOND HEAT TREATMENTCONDITION TREATMENT HEAT HEATING COOLING RATE HEAT HEATING COOLING RATECONDITION TREATMENT TEMP. HEATING TO AT LEAST TREATMENT TEMP. HEATING TOAT LEAST TEMP. TIME No. METHOD (° C.) TIME 150° C. (° C./s) METHOD (°C.) TIME 150° C. (° C./s) (° C.) (HOUR) EXAMPLE 21 BATCH 600 1 h 15CONDUCTION 350 0.96 s >=100 180 5 22 BATCH 520 3 h 15 CONDUCTION 4000.48 s >=100 180 2 23 BATCH 550 1 h 30 RUNNING 400 3.2 s >=100 160 1 24CONDUCTION 520 1.3 s >=100 RUNNING 300 15 s 15 160 5 25 RUNNING 580 2 s50 RUNNING 350 10 s 30 160 3 26 RUNNING 480 15 s 20 HIGH-FREQ. 350 0.09s >=100 140 10 27 BATCH 520 30 min 30 HIGH-FREQ. 400 1 s >=100 200 5 28BATCH 480 2 h 11 RUNNING 350 4.8 s 30 160 5 29 BATCH 500 2 h 11 BATCH400 30 s 15 200 1 30 BATCH 580 2 h 20 HIGH-FREQ. 475 0.18 s >=100 180 1031 RUNNING 480 10 s 70 CONDUCTION 350 1.3 s >=100 160 1 32 CONDUCTION500 0.24 s >=100 HIGH-FREQ. 475 0.18 s >=100 140 1 33 HIGH-FREQ. 5500.72 s >=100 CONDUCTION 400 0.24 s >=100 180 15 34 RUNNING 520 1 s 90HIGH-FREQ. 350 1.5 s >=100 200 5 35 BATCH 580 12 h 11 RUNNING 300 1 s 15220 5 36 RUNNING 620 0.5 s 20 BATCH 350 30 s 10 160 15 37 RUNNING 480 1s 50 RUNNING 350 3.2 s 50 180 10 38 RUNNING 580 10 s >=100 CONDUCTION350 0.06 s >=100 160 3 39 RUNNING 500 20 s 50 RUNNING 450 4.8 s 30 16010 40 HIGH-FREQ. 550 0.03 s >=100 CONDUCTION 400 0.12 s >=100 180 1REFERENCE LEVEL OF DISTRIBUTION PERFORMANCE VALUATION CONCENTRATION OFDENSITY OF NUMBER ADDED ELEMENTS IN Mg₂Si OF CYCLES PART OTHER THANCOMPOUND OF ELONGATION IMPACT TO COMPOUND IN PARTICLE SIZE TENSILE AFTERABSORBING FRACTURE SECTIONAL 0.5-5.0 mm STRENGTH FRACTURE CONDUCTIVITYENERGY (×10⁴ STRUCTURE (PARTICLES/μm²) (MPa) (%) (% IACS) (J/mm²)CYCLES) EXAMPLE 21 C A 305 14 44 27 132 22 C A 249 17 44 24 106 23 C A291 19 45 34 104 24 C A 271 19 36 30 112 25 C A 234 19 31 24 103 26 C A211 19 35 20 67 27 C A 256 8 54 12 86 28 C A 270 10 52 16 117 29 C A 2219 52 10 79 30 C A 267 5 47 8 215 31 C A 160 20 56 12 26 32 C A 185 22 4918 27 33 C A 205 9 55 9 60 34 A A 180 9 56 7 36 35 A A 160 9 57 5 38 36C A 273 10 46 16 117 37 C A 270 9 55 14 114 38 A A 216 15 49 17 82 39 CA 241 11 49 15 111 40 C A 231 11 47 14 83 N.B. NUMERICAL VALUES IN BOLDITALIC IN THE TABLE ARE OUT OF APPROPRIATE RANGE OF THE EXAMPLE

TABLE 3-3 AGING HEAT 1ST HEAT TREATMENT CONDITION SECOND HEAT TREATMENTCONDITION TREATMENT HEAT HEATING COOLING RATE HEAT HEATING COOLING RATECONDITION TREATMENT TEMP. HEATING TO AT LEAST TREATMENT TEMP. HEATING TOAT LEAST TEMP. TIME No. METHOD (° C.) TIME 150° C. (° C./s) METHOD (°C.) TIME 150° C. (° C./s) (° C.) (HOUR) EXAMPLE 41 CONDUCTION 550 0.03s >=100 RUNNING 400 3.2 s >=100 200 5 42 RUNNING 580 4.8 s 70 RUNNING300 4.8 s 50 160 15 43 RUNNING 480 3.2 s >=100 BATCH 350 30 s  9 160 244 RUNNING 520 3.2 s 90 RUNNING 350 4.8 s 25 140 1 45 RUNNING 520 4.8s >=100 RUNNING 350 10 s 50 180 3 46 RUNNING 620 10 s 41 RUNNING 475 0.5s 25 160 15 47 HIGH-FREQ. 580 1.5 s >=100 CONDUCTION 350 0.03 s >=100160 5 48 HIGH-FREQ. 550 0.36 s >=100 RUNNING 350 0.5 s 15 180 10 49CONDUCTION 480 0.96 s >=100 RUNNING 400 1 s 10 160 1 50 CONDUCTION 5001.8 s >=100 RUNNING 350 10 s 50 180 3 51 CONDUCTION 520 1.3 s >=100RUNNING 400 20 s >=100 160 5 52 HIGH-FREQ. 580 1 s >=100 HIGH-FREQ. 4000.36 s >=100 200 10 53 BATCH 480 2 h 30 HIGH-FREQ. 350 0.72 s >=100 1601 54 RUNNING 550 2 s 70 RUNNING 300 2 s 70 160 1 55 CONDUCTION 550 0.48s >=100 RUNNING 350 3.2 s 90 140 10 56 BATCH 550 30 min 15 CONDUCTION400 0.48 s >=100 180 5 57 BATCH 550 3 h 11 CONDUCTION 400 0.24 s >=100140 5 REFERENCE LEVEL OF DISTRIBUTION PERFORMANCE VALUATIONCONCENTRATION OF DENSITY OF NUMBER ADDED ELEMENTS IN Mg₂Si OF CYCLESPART OTHER THAN COMPOUND OF ELONGATION IMPACT TO COMPOUND IN PARTICLESIZE TENSILE AFTER ABSORBING FRACTURE SECTIONAL 0.5-5.0 mm STRENGTHFRACTURE CONDUCTIVITY ENERGY (×10³ No. STRUCTURE (PARTICLES/μm²) (MPa)(%) (% IACS) (J/mm²) CYCLES) EXAMPLE 41 C A 262 8 50 12 86 42 C A 307 946 17 135 43 C A 242 11 48 15 96 44 C A 230 18 49 22 66 45 A A 293 9 4616 112 46 C A 331 9 49 19 150 47 C A 288 11 47 19 123 48 B A 332 8 49 17153 49 C A 240 12 50 16 102 50 C A 303 8 46 15 123 51 C A 280 10 47 1794 52 C A 212 9 52 10 56 53 C A 243 17 46 23 79 54 C A 272 16 48 26 12555 B A 280 5 48 8 143 56 C A 353 5 50 12 179 57 C A 321 16 42 33 159N.B. NUMERICAL VALUES IN BOLD ITALIC IN THE TABLE ARE OUT OF APPROPRIATERANGE OF THE EXAMPLE

TABLE 4-1 AGING HEAT 1ST HEAT TREATMENT CONDITION SECOND HEAT TREATMENTCONDITION TREATMENT HEAT HEATING COOLING RATE HEAT HEATING COOLING RATECONDITION TREATMENT TEMP. HEATING TO AT LEAST TREATMENT TEMP. HEATING TOAT LEAST TEMP. TIME No. METHOD (° C.) TIME 150 (° C./s) METHOD (° C.)TIME 150 (° C./s) (° C.) (HOUR) COMPARATIVE 1 BATCH 550 1 h 15CONDUCTION 400 0.48 s >=100 160 5 EXAMPLE 2 BATCH 550 1 h 15 CONDUCTION400 0.48 s >=100 160 5 3 BATCH 550 1 h 15 CONDUCTION 400 0.48 s >=100160 5 4 BATCH 550 1 h 15 CONDUCTION 400 0.48 s >=100 160 5 5 WIRE BREAKDURING DRAWING 6 WIRE BREAK DURING DRAWING 7 WIRE BREAK DURING DRAWING 8WIRE BREAK DURING DRAWING 9 WIRE BREAK DURING DRAWING 10 BATCH 550 1 h15 CONDUCTION 400 0.48 s >=100 160 5 REFERENCE LEVEL OF DISTRIBUTIONCONCENTRATION OF DENSITY OF PERFORMANCE VALUATION ADDED ELEMENTS INMg₂Si NUMBER OF PART OTHER THAN COMPOUND OF ELONGATION IMPACT CYCLES TOCOMPOUND IN PARTICLE SIZE TENSILE AFTER ABSORBING FRACTURE SECTIONAL0.5-5.0 mm STRENGHT FRACTURE CONDUCTIVITY ENERGY (×10⁴ No. STRUCTURE(PARTICLES/μm²) (MPa) (%) (% IACS) (J/mm²) CYCLES) COMPARATIVE 1 B A 1603 45 2 16 EXAMPLE 2 B A 105 18 58 2 5 3 C A 250 3 42 4 15 4 C A 120 1655 4 6 5 — — — — — — — 6 — — — — — — — 7 — — — — — — — 8 — — — — — — — 9— — — — — — — 10 B A 265 3 26 5 16 N.B. NUMERICAL VALUES IN BOLD ITALICIN THE TABLE ARE OUT OF APPROPRIATE RANGE OF THE EXAMPLE

TABLE 4-2 AGING HEAT 1ST HEAT TREATMENT CONDITION SECOND HEAT TREATMENTCONDITION TREATMENT HEAT HEATING COOLING RATE HEAT HEATING COOLING RATECONDITION TREATMENT TEMP HEATING TO AT LEAST TREATMENT TEMP HEATING TOAT LEAST TEMP. TIME No. METHOD (° C.) TIME 150 (° C./s) METHOD (° C.)TIME 150 (° C./s) (° C.) (HOUR) COMPARATIVE 11 BATCH 550 1 h   15CONDUCTION 400 0.48 s >=100   160 5 EXAMPLE 12 BATCH

3 h FURNACE BATCH

3 h 11 160 8 COOL (LESS THAN 11° C./s) 13 BATCH

3 h FURNACE HIGH-FREQ.

0.5 s

160 12 COOL (LESS THAN 11° C./s) 14 BATCH

3 h FURNACE CONDUCTION

0.48 s

160 12 COOL (LESS THAN 11° C./s) 15 BATCH

3 h FURNACE RUNNING

30 s

160 12 COOL (LESS THAN 11° C./s) 16 CONDUCTION

0.48 s >=100 BATCH 400 30 s 15 180 1 17 BATCH 520 3 h FURNACE RUNNING400 4.8 s >=100   180 1 COOL (LESS THAN 11° C./s) 18 HIGH-FREQ. 520 0.96s >=100 BATCH

30 s 15 180 1 19 RUNNING 550 10 s >=100 BATCH 400 30 s

180 1 REFERENCE LEVEL OF DISTRIBUTION CONCENTRATION OF DENSITY OFPERFORMANCE VALUATION ADDED ELEMENTS IN Mg₂Si NUMBER OF PART OTHER THANCOMPOUND OF ELONGATION IMPACT CYCLES TO COMPOUND IN PARTICLE SIZETENSILE AFTER ABSORBING FRACTURE SECTIONAL 0.5-5.0 mm STRENGHT FRACTURECONDUCTIVITY ENERGY (×10⁴ No. STRUCTURE (PARTICLES/μm²) (MPa) (%) (%IACS) (J/mm²) CYCLES) COMPARATIVE 11 C A 95 28 63 3 5 EXAMPLE 12

A 180 4 46 1 11 13

A 190 4 51 2 9 14

A 230 3 49 2 8 15

A 290 3 47 2 12 16 B

123 17 56 5 11 17 B

120 17 57 4 11 18 D A 165 2 52 1 8 19 B B 119 15 59 4 10 N.B. NUMERICALVALUES IN BOLD ITALIC IN THE TABLE ARE OUT OF APPROPRIATE RANGE OF THEEXAMPLE

TABLE 5 NUMBER OF CYCLES TO FRACTURE No. (×10{circumflex over ( )}4CYCLES) REFERENCE  4 18 EXAMPLE  5 18  6 19  8 19  9 15 10 17 EXAMPLE 1340 18 63 20 58

The following is elucidated from the results indicated in Tables 3-1,3-2, 3-3, 4-1 and 4-2. Each of the aluminum alloy wires of Examples 1 to57 had a tensile strength, elongation and conductivity at equivalentlevels to those of the related art (aluminum alloy wire disclosed inJapanese Laid-Open Patent Publication No. 2012-229485, corresponds toComparative Example 12), and had improved impact resistance and flexfatigue resistance. In contrast, each of the aluminum alloy wires ofComparative Examples 1 to 19 has a small number of cycles to fracture of180,000 times or less, and had a reduced flex fatigue resistance. Thoseother than Comparative Examples 10 and 16 had a reduced impactresistance as well. Also, each of the Comparative Examples 5 to 9 brokeduring a wire drawing step. Each of the aluminum alloy wires ofComparative Examples 12 to 15 and 18 that has a chemical compositionwithin the range of the present disclosure, but the concentrations of Mgand Si other than compounds in a sectional structure exceeds 2.00 mass%, respectively, which are out of an appropriate range of the presentdisclosure each had a reduced flex fatigue resistance and impactresistance.

As can be seen from the results of the bending fatigue test in a hightemperature environment are indicated in Table 5, each of the aluminumalloy wire rods of Sample Nos. 13, 18 and 20, which has a composition inwhich a Mg/Si ratio is greater than 1 and Zr is an essential component,shows a number of cycles to fracture of between 400,000 and 630,000cycles, and thus has an excellent bending fatigue resistance in a hightemperature environment. Whereas, each of the aluminum alloy wire rodsof Sample Nos. 4, 5, 6, 8, 9 and 10, which are indicated as referenceexamples, does not have a composition in which a Mg/Si ratio is greaterthan 1 and Zr is an essential component. Each of the aluminum alloy wirerods of Sample Nos. 4, 5, 6, 8, 9 and 10 shows a number of cycles tofracture of between 150,000 and 190,000 cycles, and a rate of decreasein the number of cycles to fracture for the bending fatigue test in ahigh temperature environment against the number of cycles to fracturefor the bending fatigue test at an ordinary temperature was greater thanrate of decrease for Examples 13, 18 and 20.

The aluminum alloy wire rod of the present disclosure is based on aprerequisite to use an aluminum alloy containing Mg and Si, and bysuppressing the segregation (e.g., segregation within a crystal grain orsegregation at a grain boundary) at which a difference in concentrationfor each of added elements within a crystal grain or at grain boundariesin a parent phase occur due to added elements which are mainly a Mgcomponent and a Si component, and particularly when used as an extrafine wire having a strand diameter of less than or equal to 0.5 mm, analuminum alloy wire rod used as a conductor of an electric wiringstructure, an aluminum alloy stranded wire, a coated wire, a wireharness, and a method of manufacturing an aluminum alloy wire rod can beprovided with an improved impact resistance, bending fatigue resistanceand at an ordinary temperature and further with an improved bendingfatigue resistance in a high temperature environment, while ensuringstrength, elongation and conductivity equivalent to those of a productof the related art (aluminum alloy wire disclosed in Japanese Laid-OpenPatent Publication No. 2012-229485), and thus it is useful as aconducting wire for a motor, a battery cable, or a harness equipped on atransportation vehicle, and as a wiring structure of an industrialrobot. Particularly, since the aluminum alloy wire rod of the presentdisclosure has a high tensile strength, a wire size thereof can be madesmaller than that of the wire of the related art, and it can beappropriately used for a door, a trunk or a hood requiring a high impactresistance and bending fatigue resistance.

What is claimed is:
 1. An aluminum alloy wire rod having a compositioncomprising 0.1 mass % to 1.0 mass % Mg; 0.1 mass % to 1.0 mass % Si;0.01 mass % to 1.40 mass % Fe; 0.01 mass % to 0.50 mass % Zr; 0.000 mass% to 0.100 mass % Ti; 0.000 mass % to 0.030 mass % B; 0.00 mass % to1.00 mass % Cu; 0.00 mass % to 0.50 mass % Ag; 0.00 mass % to 0.50 mass% Au; 0.00 mass % to 1.00 mass % Mn; 0.00 mass % to 1.00 mass % Cr; 0.00mass % to 0.50 mass % Hf; 0.00 mass % to 0.50 mass % V; 0.00 mass % to0.50 mass % Sc; 0.00 mass % to 0.50 mass % Co; and 0.00 mass % to 0.50mass % Ni, a Mg/Si ratio being greater than 1, wherein a dispersiondensity of an Mg₂Si compound having a particle size of 0.5 μm to 5.0 μmis less than or equal to 3.0×10⁻³ particles/μm², and in a sectionalstructure, a concentration of each of Mg and Si other than a compound isless than or equal to 2.00 mass %.
 2. The aluminum alloy wire rodaccording to claim 1, wherein in the sectional structure, aconcentration of each of Fe, Ti, B, Cu, Ag, Au, Mn, Cr, Zr, Hf, V, Sc,Co and Ni other than a compound is less than or equal to 1.00 mass %. 3.The aluminum alloy wire rod according to claim 1, wherein in thesectional structure, a concentration of each of Mg, Si, Fe, Ti, B, Cu,Ag, Au, Mn, Cr, Zr, Hf, V, Sc, Co and Ni other than a compound is lessthan or equal to 1.00 mass %.
 4. The aluminum alloy wire rod accordingto claim 1, wherein the composition contains one or two element(s)selected from a group consisting of 0.001 mass % to 0.100 mass % Ti; and0.001 mass % to 0.030 mass % B.
 5. The aluminum alloy wire rod accordingto claim 1, wherein the composition contains one or more element(s)selected from a group consisting of 0.01 mass % to 1.00 mass % Cu; 0.01mass % to 0.50 mass % Ag; 0.01 mass % to 0.50 mass % Au; 0.01 mass % to1.00 mass % Mn; 0.01 mass % to 1.00 mass % Cr; 0.01 mass % to 0.50 mass% Hf; 0.01 mass % to 0.50 mass % V; 0.01 mass % to 0.50 mass % Sc; 0.01mass % to 0.50 mass % Co; and 0.01 mass % to 0.50 mass % Ni.
 6. Thealuminum alloy wire rod according to claim 1, wherein the compositionhas a sum of contents of Fe, Ti, B, Cu, Ag, Au, Mn, Cr, Zr, Hf, V, Sc,Co, and Ni of 0.02 mass % to 2.00 mass %.
 7. The aluminum alloy wire rodaccording to claim 1, wherein an impact absorption energy is greaterthan or equal to 5 J/mm².
 8. The aluminum alloy wire rod according toclaim 1, wherein number of cycles to fracture measured in a bendingfatigue test at an ordinary temperature is greater than or equal to200,000 cycles.
 9. The aluminum alloy wire rod according to claim 1,wherein number of cycles to fracture measured in a bending fatigue testin a constant temperature tank at a temperature of 120° C. is 400,000cycles to 630,000 cycles.
 10. The aluminum alloy wire rod according toclaim 1, wherein the aluminum alloy wire rod is an aluminum alloy wirehaving a diameter of 0.1 mm to 0.5 mm.
 11. An aluminum alloy strandedwire comprising a plurality of aluminum alloy wire rods as claimed inclaim 10 which are stranded together.
 12. A coated wire comprising acoating layer at an outer periphery of the aluminum alloy wire rod asclaimed in claim
 10. 13. A coated wire comprising a coating layer at anouter periphery of the aluminum alloy stranded wire as claimed in claim11.
 14. A wire harness comprising: a coated wire including a coatinglayer at an outer periphery of one of an aluminum alloy wire rod and analuminum alloy stranded wire, the aluminum alloy stranded wirecomprising a plurality of the aluminum alloy wire rods which arestranded together; and a terminal fitted at an end portion of the coatedwire, the coating layer being removed from the end portion, the aluminumalloy wire rod having a composition comprising 0.1 mass % to 1.0 mass %Mg, 0.1 mass % to 1.0 mass % Si; 0.01 mass % to 1.40 mass % Fe; 0.01mass % to 0.50 mass % Zr; 0.000 mass % to 0.100 mass % Ti; 0.000 mass %to 0.030 mass % B; 0.00 mass % to 1.00 mass % Cu; 0.00 mass % to 0.50mass % Ag; 0.00 mass % to 0.50 mass % Au; 0.00 mass % to 1.00 mass % Mn;0.00 mass % to 1.00 mass % Cr; 0.00 mass % to 0.50 mass % Hf; 0.00 mass% to 0.50 mass % V; 0.00 mass % to 0.50 mass % Sc; 0.00 mass % to 0.50mass % Co; and 0.00 mass % to 0.50 mass % Ni, a Mg/Si ratio beinggreater than 1, wherein a dispersion density of an Mg₂Si compound havinga particle size of 0.5 μm to 5.0 μm is less than or equal to 3.0×10⁻³particles/μm², and in a sectional structure, a concentration of each ofMg and Si other than a compound is less than or equal to 2.00 mass %.15. A method of manufacturing an aluminum alloy wire rod as claimed inclaim 1, the aluminum alloy wire rod being obtained by forming a drawingstock through hot working subsequent to melting and casting, andthereafter carrying out processes including a first wire drawingprocess, a first heat treatment process, a second wire drawing process,a second heat treatment process and an aging heat treatment process inthis order, wherein the first heat treatment process includes, afterheating to a predetermined temperature within a range of 480° C. to 620°C., cooling at an average cooling rate of greater than or equal to 10°C./s at least to a temperature of 150° C., and the second heat treatmentincludes, after heating to a predetermined temperature within a range ofhigher than or equal to 300° C. and lower than 480° C. for less than twominutes, cooling at an average cooling rate of greater than or equal to9° C./s at least to a temperature of 150° C.